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problem with led’s

Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=110238
Printed Date: May 14, 2025 at 9:13 AM


Topic: problem with led’s

Posted By: adamtaylorpcb
Subject: problem with led’s
Date Posted: January 01, 2009 at 7:19 PM

i found several small 3 led clusters in the shop while cleaning it out. i ran wires off of the leads and tried it on a 12v source and nothing happened. not much experience with leds. do i need to put a resistor or something on them or are they blown



Replies:

Posted By: ckeeler
Date Posted: January 02, 2009 at 11:27 AM
they are most likely burnt out. when you connected them did they flash on for just a brief second, and then nothing? if so you burned them out when you connected them. especially if you did not connect them with a resistor.



Posted By: adamtaylorpcb
Date Posted: January 02, 2009 at 12:14 PM
yeah, the one i tried did that

how will i find out what resistor i need?



Posted By: ckeeler
Date Posted: January 02, 2009 at 12:30 PM
Do you know anything about them? how many are in each cluster? 3?



Posted By: KPierson
Date Posted: January 02, 2009 at 1:40 PM

What are you trying to get the LEDs to do?  With three LEDs you should be more then safe to run a 1K resistor in series with the cluster.  You can then gradually step down the resistance size if you want the LEDs to be brighter.

The proper way to size the resistor is to use the forward current rating of the specific LED you are using.  However, since it is unlikely you know the part number of the LEDs you will just have to experament a bit.



-------------
Kevin Pierson


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